Electric motors are well known in the art and have been put to use in a variety of applications, including the handling of air. In this circumstance, an electric motor is coupled to a fan, creating a motor-fan unit, which produces an airflow as needed. When providing air movement, the motor-fan unit may supply cooling air to the motor, so as to maintain the motor's operating temperature at an optimal level, allowing the motor's operating life to be extended. The motor-fan unit may also be used to generate working air for vacuum type devices.
To achieve this effect, the fan is mounted on a motor driven shaft, which draws air into a fan shroud. The fan shroud compresses or pressurizes the incoming air, which is resultantly released into the motor housing via one or more ports in a diffuser plate, causing the air to be directed toward the motor windings. As a result, the heat from the motor is drawn into the airflow and exhausted from the motor housing, thus enhancing the motor's operating life. In other embodiments, air passing through the diffuser plate may be collected and routed through a single radial and tangentially extending exhaust port.
In order to efficiently operate the motor-fan assembly, it is important to have efficient air flow through the assembly. In this regard, it has been determined that prior art fan constructions may utilize flat fan rings and a flat fan disc which are parallel to one another and connected to one another by a plurality of curvilinear vanes. This has been improved upon by providing a tapered or convex fan ring and a flat fan ring which allows for more collection of air within the fan before it is exhausted out through the diffuser and a motor assembly. However, it is believed that such a configuration is not as efficient as it could be. Indeed, after the air is drawn into the fan through the fan ring, the collected air is required to make a sharp right angle turn by the flat fan ring. And it is believed that the convex ring/flat disc configuration allows for “dead space” to form within the confines of the fan. This allows small turbulent air currents to develop within the fan assembly as it rotates. These small air currents interfere with or flow against the predominate air flow pattern. Moreover, at some rotational speeds, the sharp turning of the air and resulting turbulent air currents causes air to back up and significantly slow entry of air into the fan. As a result, the fan vanes generate additional noise further hindering performance of the motor-fan assembly. As such, air does not efficiently move through the fan assembly, causing the motor assembly to work harder and consume more power. Moreover, the small air currents that exist within the fan unit may allow for dust and water-born debris to accumulate around the connection between the fan assembly and a motor shaft. As such, this accumulation of moisture may migrate into the bearing area and cause the bearing to abnormally degrade.
Another detriment to fan assemblies which utilize a rotating fan with a flat fan ring is that the length of the motor shaft is extended. At critical speeds, an extended length motor shaft begins to flex resulting in significant operational deficiencies.
Therefore, there is a need for a motor-fan unit a fan assembly that utilizes a tapered fan having a concave underside. Such a configuration allows for efficient movement of air through the fan assembly without generation of deleterious airflow patterns. In other words, there is a need for a fan which moves air through the fan assembly without any lingering air current flows developing which would adversely effect operation of the motor-fan unit. And there is a need for a motor-fan unit which decreases the axial length of the motor to reduce shaft flexing and improve performance of the motor.